A survival game set in a lush rainforest, Green Hell has a lot to like. As of this writing I've only played through the main story on "Welcome to the Jungle" difficulty, so I'm unfamiliar with what differences are present in the Spirits of Amazonia mode (which is said to be a prequel to the main story) and Survival mode, but I had a great time and found it to be very immersive with just the right amount of challenge.
I enjoyed how there's not just one gauge for food but four separate satiety gauges (protein, carbohydrates, fats, and water). Becoming deficient in one or more doesn't spell instant death, but it does make things more difficult as it limits your maximum health. Being attacked by a wild animal while traversing the wilderness in a malnourished state can quickly put an end to an expedition where you may otherwise be able to bandage yourself up and press on.
Managing your inventory (not just weight, but space) is fairly straight forward. You have a backpack which is separated into sections accommodating different types of items: tools/weapons, sticks and rope, materials, food/consumables, and items for starting fires. One nice touch that makes items feel like physical objects is that you can grab anything in the world and seamlessly drag it to and from your backpack, even holding it in your "hands" while moving, though it can be a bit clumsy to navigate the world while doing so (this came in handy a lot when I wanted to grab just one more thing but couldn't fit it in). Early on I found playing inventory Tetris a bit tedious but I found that there's an auto-sort function hidden in the keybinds section, which should probably be displayed in the inventory UI.
Another UI touch I liked was the use of the notebook as the primary menu. Objectives, crafting recipes, and the effects of the various plants you find (and name) are recorded inside. Flicking through the pages of the notebook makes the game just a bit more immersive than clicking through some sterile menus.
As a survival crafting type of game, there's of course a lot of crafting. You craft things by dragging them from your backpack to the crafting area. As your crafting skill improves, some recipes will be unlocked but many items can be constructed just by experimenting with different combinations of materials. When you drag materials into the crafting area, small circles indicate how many additional materials are part of a valid recipe and these circles fill up as you pick the correct materials.
You can also build structures with various utilities such as storage bins, beds, different types of food preparation facilities, garden plots, and so on. The recipes for these must be discovered in the world, which adds them to your notebook.
In addition to the "usable" structures, you can and should construct shelter (which is needed for saving, more on that later). For basic shelter you can build a small hut or lean-to, but there is also a more elaborate modular construction system which involves building frames, to which you can attach walls, ladders, roofs, or even multiple floors. It's a fairly intuitive system and usually the game is good about showing if a plant is obstructing something, though sometimes where buildings can be placed is prohibited for unknown reasons. Some structures have multiple variants available based on material, for example you may build a shelter with palm leaves or banana leaves, or build a wall with wood or with mud bricks.
I was confused at first by the saving system; since I found natural shelter in a cave I assumed a bed would allow me to save the game. However, beds only satisfy the need for rest, to save you need to build shelter. There are some small shelter structures that have a bed and thus allow both saving and sleeping; other structures, and the modular buildings, require a bed to be built separately to be able to sleep. Thankfully, the game has a save and quit function for times where you need to leave the game right away (like me, playing the game and realising it's 3 AM and I'm nowhere near my home camp).
Shelter (natural or man-made) will also protect fire from the rain. Fire is useful for cooking, boiling water to render it safe to drink, and staving off worms that may burrow into your flesh while you sleep. This lead to me scrambling in the dark to hastily throw together a hut, far from home, which was a really fun experience.
The lush rainforest is great to look at. I especially like the nights where you see the beams of moonlight streaming through the leaves above. The sound design adds to the visuals to make a really immersive experience; the rustling of leaves never failed to make me look behind me and the sounds of wildlife was calming (or terrifying, in the case of the low growl of a jaguar).
I won't go into the story because it's the kind of story that benefits from surprise, but I enjoyed it a lot more than I expected of a story in a game of this genre. It's fairly low on cutscenes and most exposition is done through dialogues via radio and notes you can find in the environment. The game doesn't offer precise directions for progressing the story, rather, you get hints at where to go or what to do next recorded in your notebook. For the most part this works well and it got me to explore almost the entirety of the map, with just two stumbling blocks at the end of the game that I had to look up.